Electroanalysis of tert-butylhydroquinone in edible oil at a Nafion-coatedprobe

An electrochemical probe consisting of co-planar platinum working and count er electrodes, and a silver quasi-reference electrode, was coated with a fi lm of ionically conducting polymer, Nafion. The electrochemical behavior of ferrocene in a cooking oil could be observed at the probe without sample p retreatment. Hence it was demonstrated that the probe could be used to perf orm direct analysis of the antioxidant tert-butylhydroquinone (TBHQ) in edi ble oils. Using differential pulse voltammetry (DPV), a linear response to TBHQ was obtained across the concentration range 1-50 mg kg(-1), with a sen sitivity of 6.49 x 10(-11) A kg mg-l the detection time being 2 min for eac h assay. The limit of detection was 0.25 mg kg(-1) (S/N = 3). Interference from phenolic antioxidants such as tert-butylhydroxyanisole (BHA), tertbuty lhydroxytoluene (BHT), propylene glycol, and propyl gallate was studied. BH A showed some interference at TBHQ:BHA ratios of 1.1 and 1:2. The others di d not interfere. The mean recoveries of TBHQ spiked into samples of soybean , sunflower and palm oil were found to be 96%, 102% and 102%, respectively (n = 5).